I'm not too sure, but what i heard from my sis (graduated from nutrition and dietetics this yr at monash) and from friends plus personal experience (on course transfer at monash), u could try to get into biomedical science or science to start off with and take up a chemistry subject..... check it with the faculty to c which chem subject u need to do to qualify into the dietetics.
In addition i dun think the dietetics course at monash actually allow any transfer from other courses which is not related to dietetics at all. Mainly due to the small amount of intake but once you finish the biomedical science or science course and provided u satisfactory completing the prerequisite required (again check the monash handbook or with the faculty + D avg in terms of marks, you can apply into the dietetics course (known as graduate transfer) with the fact that u will be starting in 3rd yr since u would have cover most of the basic medical units during the previous biomedical degree.
However this info is only applicable for monash, i am not sure how deakin works. What i'm sure is without the yr 12 chem prerequisite, they will not consider you as an apllicant for now. Should u need any more info i would be happy to provide. PM me if this is the case. Good luck with ur pref.